Rotary variable electrical resistance devices, eg. potentiometers, are well known in the art. Such a device typically comprises a housing containing an arcuate element of electrical resistance material adapted to be traversed by a wiper of electrically conductive material, the wiper being operated by a rotatable spindle which is supported on bearings in the housing. Adjustment of the setting of the device is effected by rotating part of the spindle which protrudes from the housing. It has hitherto been common practice to mount a variable resistance device with its housing rigidly secured to a support which may, for example, be a rigid plate having a hole through which the operating spindle of the device passes.
It is sometimes required to couple the spindle of a variable resistance device to an operating shaft in order to provide an extension to the spindle or to monitor the degree of rotation of such a shaft. Problems exist in accurately aligning the shaft and spindle and also the shaft may not be absolutely straight. The shaft may also be mounted in such a way that it can exhibit a significant degree of axial and radial play. If a solid coupling is used between the shaft and spindle with any of these conditions existing, then the bearings of the spindle in the housing of the device may be subjected to excessive forces, resulting in damage to the device. Variations in torque in the shaft/spindle assembly may also occur during rotation in these conditions.
It has previously been proposed to deal with this problem by coupling the shaft and the spindle of the device by means of a flexible coupling member. Such a flexible coupling is expensive and often bulky to the extent that insufficient space is available for it to be used in some applications.